$ perl -de 42

Loading DB routines from perl5db.pl version 1.33
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):   42
  DB<1> opendir $dirh, "Old_PL_programs" or die "could not open dir $!";

  DB<2> @list_files = readdir $dirh;

  DB<3> print " @list_files";
 . .. 24.pl 2tab.pl aa.pl ack_nomem.pl [... many files omitted] VAR.pl walk_HoA.pl whitespace.pl xml.pl zip_read.pl
  DB<4> foreach $file ( @list_files) {print $file, "\n" if 50 > -M "Old_PL_programs/$file;"}; # prints files younger than 50 days
ack_nomem.pl
fringe.pl
khalou2.pl

##</code><code>##

  DB<6> print join "\n", grep { -M $_ < 50 } glob ("Old_PL_programs/*.*");
Old_PL_programs/ack_nomem.pl
Old_PL_programs/fringe.pl
Old_PL_programs/khalou2.pl

##</code><code>##

  DB<7> print join "\n", map {s/^.*\/(.+)/$1/r} grep -M $_<50, glob ("Old_PL_programs/*.*");
ack_nomem.pl
fringe.pl
khalou2.pl

##</code><code>##

  DB<7> print map {s/^.*\/(.+)/$1/; "$_\n"} grep -M $_<50, glob ("Old_PL_programs/*.*");